The invention relates to active implantable medical devices, as defined by Directive 90/385/EEC of 20 Jun. 1990 of the Council of the European Communities.
These devices include an implantable generator containing in a housing various electronic circuits, a battery and a connector head for the coupling of the generator to various leads provided with electrodes for detecting electrical potentials at a remote location and/or for delivering stimulation pulses.
At the time of implantation, the leads are mechanically connected and electrically connected to the generator via plug sockets that are inserted into the connector of the generator so as to connect different contacts of these plugs to homologous terminals of the internal circuit of the generator.
The leads may be leads directly and separately connected to the generator, as well as indirectly connected by an intermediate accessory connecting various leads to a common, multipolar connector of the generator. Each of the leads are connected to internal terminals of the circuit of the generator, the circuit having the same number of terminals as the number of leads, or the electrodes of the leads.
The disclosure relates more particularly to those devices which enable both:
by one or more intracardiac or epicardial “cardiac” leads, detection of depolarization potentials of the myocardium (“cardiac potentials”) and/or to deliver to the heart electrical stimulation, defibrillation or resynchronization pulses (“cardiac pacing pulses”). These functions of detection and/or delivery of pulses in relation with the heart will hereinafter be collectively referred to as “cardiac therapy.” The documents US 2010/137929 A1, EP 2402054 A1, U.S. Pat. No. 6,317,633 B1, FR 2,558,732 A1, US 2012/123496 A1 and US 2011/224988 A1 describe examples of such devices, which may include a plurality of cardiac detection/stimulation leads provided with electrodes located in or on the heart; and
by one or more “peripheral leads” implanted on a “peripheral anatomical structure” (e.g., organ) other than the heart, to detect depolarization potentials (“peripheral” potentials) and/or to issue to the peripheral anatomical structure stimulation pulses (“peripheral” pulses). The peripheral pulses may be different from those delivered to the heart both by their nature and their sequencing. These functions of detection and/or delivery of pacing pulses in relation to the peripheral anatomical structures will hereafter be collectively referred to as “peripheral therapy.”
The peripheral anatomical structure may be, for example and without limitation, a nerve, especially the vagus nerve, the brain, a muscle, etc. The therapy device can be in particular, and without limitation, stimulation therapy to the vagus nerve (VNS), stimulation of the spinal cord (SCS), deep brain stimulation (DBS), stimulation of a peripheral nerve (PNS), carotid stimulation (CBS), muscle stimulation (MS), etc. Direct stimulation of the nervous system is often referred to as neuromodulation.
EP 2179764 A2 describes such a device capable of delivering two therapies of different nature simultaneously, from respective stimulation channels, which may optionally be grouped in the same generator housing.
Such a device requires at least two leads which are also of different nature (one or more lead(s) for the cardiac therapy and one or more other lead(s) for the peripheral therapy).
For practical reasons, it may be desirable to have identical connectors for all of the leads connected to the generator, irrespective of their function. The availability of identical connectors, for example IS-1 connectors, simplifies the design of the generator and of the leads, to optimize the usability by using already available leads, etc.
This method therefore introduces a risk of incorrect placement of leads within the generator plugs during the implantation procedure. In the case of lead connection error, the cardiac pacing pulses and peripheral stimulation delivered by the generator will be applied to the wrong target (the heart instead of the peripheral anatomical structure and vice versa), or will not be applied at all. The lead connector error may present risks for the patient. For example, when a peripheral therapy is applied to the heart, the therapy could induce tachycardia or even fibrillation depending on the energy and frequency of the delivered pulses.
There are various known generators able to automatically detect the insertion of a lead and to subsequently activate various features, initialize a number of parameters, store initial data for implantation, etc.
These devices typically operate by measuring the impedance between the generator terminals of the connector. In the absence of a lead this impedance is very high, but upon insertion of a lead, the value decreases below a certain threshold, the crossing of the threshold is detected causing the generator to change the mode of operation of the pacemaker from a standby mode to a fully functional mode.
A continuous scan of the impedance, however, is disadvantageous in terms of consumption and lifetime of the battery, because it requires, at each measurement, the injection of current and the activation of circuits for measuring the corresponding collected voltage. It is therefore not desirable to operate a continuous scan, particularly in the commercial use of the generator. Moreover, the use of an automatic impedance measurement for certain peripheral leads may be undesirable.
EP 1618923 A1 (Sorin CRM) discloses another technique of detecting a lead, which does not require the direct and continuous measurement of the impedance between the terminals of the generator. This technique is only to monitor the consumption of the device. Any modification of the consumption revealing a change in behavior of the device, is generally due to the connection of a lead and the implantation of the lead due to: i) stimulation on a charge that is no longer infinite (as was the case in the commercial use), ii) detection of cardiac signals activating the digital filters whose consumption depends on the input signal, and iii) wake-up of microcontroller running specific software instructions on each new detection. The device described in EP 1618923 A1 also determines the type of lead used (monopolar or bipolar) and automatically adapts the various circuits and algorithms of the device according to the type of lead. This function minimizes any risk of error resulting in a defect which may, for example, cause the application of a bipolar stimulation to a monopolar lead.
However, this device, which is based on the specificities of cardiac leads and signals, cannot be applied to a mixed generator capable of delivering both a cardiac therapy and a peripheral therapy. The two targets (heart and peripheral anatomical structure) are very different in nature. The cardiac therapy generator could distinguish a bipolar cardiac lead from a monopolar cardiac lead, but may not be able to tell the difference between a cardiac lead and a peripheral lead, or between a peripheral lead and the absence of a lead. The device could also tell the difference between an absence of lead and the presence of a lead (by the impedance measurement), but would not know if the lead is a cardiac lead or a peripheral lead.
The technique described in EP 1618923 A1 is limited to the verification of the connection of leads and to the correct setting of the generator depending on the type (monopolar or bipolar) of lead. It does not restore as appropriate a misconfiguration, or does not leave the option for the practitioner to connect the leads of various natures to the generator in a completely interchangeable method, while leaving the latter to automatically establish the correct connection scheme, irrespective of the manner in which leads were inserted on the generator.